In recent years, with the enhancement achieved in the communication speed and the progress made in cloud computing, there has been a sudden expansion in the use of near field communication (NFC). Typically, the NEC is implemented in IC cards such as cash cards or credit cards; in the electronic money facility provided in smartphones; and in smart cards used as bus tickets or railway tickets. In the NFC, the issue has been to strengthen the security in regard to the ID identification function that enables identification of individual persons.
Besides, in recent years, even the memory cards that were typically used only to store personal data are also increasingly being equipped with the ID identification function. That has led to the technical issue of providing sophisticated ID identification function in portable devices.
With that background, research and development has been going on about using the variability in each individual device as the “chip fingerprint”. Such technology is known as a physically unclonable function (PUF).
From among the types of PUF, the PUF that is most researched at present is SEAM-PUP (SRAM stands for static random access memory). The SRAM-PUF represents the technology for using the variability that exists while manufacturing two inverters constituting an SRAM. Particularly, the RAM-PUF[1-3] that is most popular is implemented in the security IP and IC cards mentioned above. Moreover, as a proposal for using the initial variability of an electronic device, the application of PUF to a nonvolatile memory is also being studied.